WORCESTER — Authorities believe a truck making a delivery of some sort of chemical compound in an industrial area Tuesday inadvertently dropped an unknown white, powdery but non-toxic substance on two sections of Fremont Street.

District Fire Chief Frank DiLiddo said several residents in the area called to report the spill about 10 a.m., and firefighters responded. District Chief DiLiddo requested a Tier 1 response from the state Department of Fire Services hazardous materials response team to help assess how dangerous the white substance was.

Fremont Street was closed between Cambridge and Webster streets until about 6 p.m. to allow state environmental crews to clean up the spill. The incident forced the Worcester Regional Transit Authority to detour buses.

A 100-foot-long ribbon of white powder went along the middle of Fremont just past Applied Plastic Technology, 169 Fremont St. Crews also had to clean up a 200-foot stretch of Fremont Street closer to Webster Street.

Ed Coletta, a spokesman for the state Department of Environmental Protection, said the substance appeared to be a silicate of some type but was not corrosive, flammable or reactive.

"We really don't know what it is at this time," he said. "But it isn't a threat to the environment."

He said a state contractor was on scene putting the substance into containers for future disposal.

The spill was in an industrial area with several chemical plants and automotive businesses.

Chief DiLiddo said authorities canvassed all neighborhood businesses to see if any of them had received a delivery Tuesday morning, if any had sent out a truck.

"None of the businesses said they had deliveries," District Chief DiLiddo said. He said firefighters performed preliminary testing with pH papers and gas meters. "The substance was not giving off any type of telltale signs."

Fire Lt. Paul LaRochelle wore a mask that covered his entire face as he collected a container of the white substance. Techs from the state's hazmat team used sophisticated equipment to determine the compound is not toxic.

"I just want to stay far away from whatever it is," said Raymond Lewis of 166 Fremont St. He had walked out of his apartment with his 1-year-old daughter and had been just about to head down the sidewalk when he saw a police cruiser up the road, yellow tape blocking off the roadway and firetrucks at the corner of Fremont and Cambridge streets. He did not stay outside. He said, "I'm just worried about my daughter."

Another neighbor, Tim Hast, said, "Trucks go up and down this road all day."

District Fire Chief DiLiddo said the large quantity of the bulk substance came from a transportation container. He said state Department of Environmental had on-call crews remove the crystal-like substance in 55-gallon drums. He said the substance was non-reactive with water.

"No toxins were given off," District Chief DiLiddo said.

Brian Fenner lives on Fremont Street, and said he was grateful for the precautions that Fire Department took.